Having completed the Civil War quest line for the imperials, it was mentioned in passing that I might meet Stormcloaks out in the wilderness and I should do my best to dispatch them.
However, the two Stormcloak camps that I have happened upon and assaulted have had immortal named NPCs in them (I assume quest-givers for "the other side"). I have killed all the foot soldiers in the camp (including the wounded in hospitals for good measure) and even emptied all the chests, however the named NPCs just refuse to get off their knees and die with dignity.
Is clearing the camps themselves an impossible task?